Problem: $ { {-1} \times \left[\begin{array}{rr}{2} & {2} \\ {3} & {4}\end{array}\right] = {?} } $
Answer: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{-1}\times{2} & {-1}\times{2} \\ {-1}\times{3} & {-1}\times{4}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{-2} & {-2} \\ {-3} & {-4}\end{array}\right]}$